In some cases, overactive lip depressors, or dental issues can cause this look. Botox can be used to weaken the lip depressors, which then lets the lip elevator muscles lift the lip .
The infra-mammary fold approach can easily be done with a dual plane placement of the implant. This is very common. The periareolar approach is good if you also need a peri-areolar lift or just want to hide the scar there. The downside is closer to the milk ducts so there can be more bacterial contamination and slightly higher risk of infection.
Many women loose all support and elasticity of their breast skin after massive weight loss. The best option is to restructure the skin envelope into a smaller perkier skin shape, and then fill that volume with either an implant or even your own adipose tissue from liposuction from another part of your body.
The long part of the scar is hidden where your underwire sits, and takes a little more time to heal, but the shape improvement just can't be beat.
Going too big in skin that is already stretched can lead to more problems down the road. If you don't want the extra scars, you could just fill the space you have . If you do go that large, make sure you are wearing a supportive bra during the day and support at night.
You have some gravitational descent and skin laxity. A combination augmentation with a subtle peri-areolar mastopexy could give you a nice natural result while hiding the scar around the edge of the areola. Gel implants feel so much more natural, with less rippling, and are better suited in the subglandualr plane ( less pain, less dissection and less distortion if you work out your pectoral muscles). Treat yourself !